Despite this being the "General" discussion board, we do generally only help with the mIRC client or IRC in general. Finding files on IRC is, on the most part, against the law, dangerous and against network rules.
Whilst I'm unsure about what OST stands for, I think it means Opening Sound Track. In which case, you may want to search
Google for any sites which may contain music clips or if you're able to download music songs at a cheaper price. Of course, although more inconvenient for us lazy bones, Macondo's suggestions is the more practical.
Good luck finding it, and let us know if we haven't helped you in any way =)
Regards,
